Microelectrode recordings from trigeminal nuclei of caudalis are performed in anesthetized monkeys. Mechanical and thermal stimuli, both in the noxious and non-noxious range, are applied to the face and oral mucosa and the response properties of single neurons are recorded and stored on magnetic tape. These neurons are also analyzed with respect to whether they project to the thalamus. Data is analyzed with an on-line, real-time computer system.